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std 10 science chapter 1 gravitation explanation


Std 10 science chapter 1 gravitation explanation



 1. Gravitation
 
                      
std 10 science chapter 1 gravitation explanation
std 10 science chapter gravitation explanation1 

                                                 std 10 science chapter 1 gravitation explanation
    When an object gets attract toward another object because of it has a lower mass than the object who has higher mass. The attraction between the two objects are called gravitation.
     Gravitation was first discovered by Sir Isaac Newton. As he was sitting below the apple tree one apple fell from a tree on the ground. Then he thought that why apple is falling down? Why it is not going upward direction. This incident led him to find gravity.

Gravitational force definition: The force of attraction between two objects which led one object to move toward another object is called gravitational force.

Force and motion: an effect tending to change the motion of the body or produce motion in the stationary object is called force. When an object moves from one place to another is called motion.

Circular motion: Circular motion is the motion of a particle along with the circumference of the circle is known as circular motion.

Centripetal force: It is a force acting on a particle performing circular motion which is acting along the radius of a circle and directed toward the centre of the circle is called the centripetal force.

Kepler’s Laws: Planetary motion had been observed since long time ago. Before the invention of the telescope in the 16th century, all observation made with naked eyes. Lots of data were collected. Johannes Kepler studied the data and gave three laws of planetary motion.

  Kepler’s first law: The orbits of a planet is an ellipse (oval) with the sun at one of the foci (plural form of focus).

  Kepler’s second law: While revolving around the sun, planet covers the equal area in equal an interval of time.

  Kepler’s third law: The Square of its time of revolution around the sun is directly proportional to the cube of the mean the distance thus if ‘r’ and ‘T’ is period of revolution then T2αr3 i.e. T2/r3=constant=K

Newton’s universal law of gravitation: It says that this force is directly proportional  product of masses and inversely proportional to Square of the distance between them.
F=Gm1m2/d2
Here G is constant and is called the universal gravitational constant.
The value of G is always 6.673*10 Nm2 kg-2.

Earth gravitational force: when we throw stone vertically upward it goes up to a certain distance and fall down on ground back. It happens because of the earth gravitational force. Earth attracts every object toward itself because of its gravitational force. And because of this force, every object falls vertically to the ground. When the stone goes up it is affected by earth gravity this led the stone to reduce its velocity continuously. And when the velocity of stone become zero it falls vertically toward earth.
Always remember  Mass of earth=6*1024kg.
                                    The radius of the earth=6.4*106m.

Earth’s gravitational acceleration: The acceleration produced in the body under the effect of Gravity or Gravitational force is called acceleration due to gravity. It is denoted by g.
The value of g=9.77m/s2.
The value of g is constantly changing according to the height of the object.
The value of g is also changed along the surface of the earth: As the shape of the earth is not exactly sphere at some point there is high and some point there is low so this led to change in height of the object in surface to the centre of the earth. The earth radius is higher at the equator and lower at the poles thus, the value of g is highest at poles (9.832m/s2) and lowest at the equator (9.78m/s2).

The value of g change with height: As we go higher in the sky from the centre of the earth the height increase from the earth and as we know that height is inversely proportional gravitation hence when an object goes high gravitation force decreases. But it acts on a certain height forex. If we go 10 km up then the value of g is negligible. On the another way if we consider the satellite which orbiting to the earth for them the value of g is low because they are at a very high height from the centre of earth.

  The value of g in different places:


Place
Height(km)
G(m/s2)
The surface of the earth (average)
0
9.8
Mount Everest
8.8
9.8
The maximum height reached by man-made balloon
36.6
9.77
Height of typical weather satellite
400
8.7
Height of communication satellite
35700
0.225

Change with depth: The value of also change with depth as we go inside the earth. You must think that if we go inside the earth the value of increase but it not. Because the part of the earth contributes mass for gravitation is not present because we go inside the earth which means the mass of the earth is less and hence the force of gravitation is less.

What is meant by escape Velocity:

The minimum the velocity with which satellite should be Projected from the surface of the earth so that its escapes from the earth is called escape velocity.
 These all are the easiest definition of the physics fundamentals.

Escape velocity formula:  


Introduction to scientist:

Sir Issac newton


std 10 science chapter 1 gravitation explanation
Issac Newton


Great scientists:  Sir Issac Newton (1642-1727) was one of the greatest scientists of recent time. He was
born in England. He gave his law of motion, equation of motion and theory of gravity in his book Principia. Before this book was written, Kepler had given three laws describing planetary motions. However, the reason why the planet moves in the way described by Kepler's laws was not known. Newton, with his theory of gravity, mathematically derived Kepler's laws. In addition to this, Newton did groundbreaking work in several areas including light, heat, sound and mathematics. He invented a new branch of mathematics. This is called calculus and has wide-ranging application in physics application and mathematics. This is called calculus and has wide-ranging applications in physics and mathematics. He was the first scientist to construct a reflecting Telescope.

Johannes Kepler:

std 10 science chapter 1 gravitation explanation
Johannes Kepler

Johannes Kepler (1571-1630) was a German astronomer and mathematician. He started working as a helper to the famous Astronomer Tycho Brahe in Prague in 1600. After the sudden death of Brahe in 1601. Kepler was appointed as the Royal mathematician in his place. Kepler used the observations of planetary positions made by Brahe to discover the laws of planetary motion. He wrote several books. His work was later used by Newton in postulating his law of gravitation.

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